DE 100 57 759 A1 describes a rear window shade for motor vehicles. This rear window shade comprises a winding shaft that is rotatably supported underneath a rear window shelf, wherein one edge of the strip-shaped shade is fixed the winding shaft. The strip-shaped shade is cut into an approximately trapezoidal shape with its other end distant to the winding shaft fixed to a draw-out rod Movement of the draw-out rod is laterally guided in two guide rails that are either bonded to the inner side of the rear window or hidden in the car body behind the lining of a C-column. Elastically bendable thrust elements for moving the draw-out rod are guided in the guide rails in a buckle-proof fashion.
The guide rails consist of an extruded aluminum profile with a continuous undercut groove. The groove is composed of a section with a circular cross section and a section with a rectangular cross section, wherein the section with a rectangular cross section is narrower than the diameter of the circle. The rectangular section forms a slot that opens the guide groove in the outward direction.
Sliding or guiding elements move in the guide rails the sliding or guiding elements have a head, the cross section of which is adapted to the circular section of the guide rail profile. This head has the shape of a ball or a short cylindrical section, with dimensions such that it cannot become jammed in the curved sections of the guide rails. A diameter of a neck of the sliding or guiding elements is chosen such that it fits through the slot of the guide groove without getting stuck.
The head of the guiding element usually is an injection-molded plastic part. Long-term usage has revealed that the combination of the plastic part and an aluminum rail is not rattle-free under all conditions. The friction between the plastic guide elements and the aluminum guide rail is not suited for optimal relative movement. In addition, certain difficulties can occur when integrating the guide rail into the inside lining.